“There’s a real galvanization of all the groups this year,” said Fernanda Durand of CASA in Action, which will lead a march of about 10,000 people for immigrants' rights through downtown Washington. “Our presence in this country is being questioned by Donald Trump. We are tired of being demonized and scapegoated. We’ve had enough.”
Durand’s protest is part of the Rise Up umbrella movement that promises 259 events in more than 200 cities in 41 states focusing on immigrants' rights, she said.
Another widespread effort, dubbed Beyond the Movement, will feature a collection of racial-justice groups and include protests and marches in more than 50 cities, from Portland, Ore., to Miami. 
Erick Sanchez, another Washington-based organizer, said he’s seen the melding of different groups in previous events this year, from the Women’s March on Washington to climate change awareness protests. Monday will be the culmination of gelling these disparate groups, he said.
“There’s really a sense that we’re in this together,” he said. “That an attack on one is an attack on all.”
Trump released a statement Friday declaring May 1 “Loyalty Day” as a way to “recognize and reaffirm our allegiance to the principles” upon which America was built, calling on all government buildings to display the U.S. flag and schools to observe the holiday with ceremonies.
The holiday has been proclaimed by every president since Dwight D. Eisenhower, on differing dates, but Trump’s critics skewered the timing of the proclamation on social media.
Wrote @LibyaLiberty: “They said 'Loyalty Day' is to uphold 'the inherent dignity of every human being' -- a few days after launching a hotline for 'removable aliens'”
“If I were like, the worst president ever & wanted to make my critics look like traitors, I would declare May 1st Loyalty Day,” wrote @Onision.
Originally a pagan celebration dating back two millenniums and heralding the return of spring, May Day has morphed into a global observance of workers’ rights. But its emergence as an international worker’s rights day actually arose from a May 1, 1886, Chicago strike for the eight-hour workday.
“The fight for leisure — clearly lost today — was a great unifying aspiration of the immigrant workers movement a century ago with its slogan, ‘eight hours for work, eight hours for sleep, eight hours for what we will,’” Nelson Lichtenstein, professor of history at the University of California, Santa Barbara, and director of the Center for the Study of Work, Labor, and Democracy, wrote in a 2006 essay in Slate.com.
Demonstrations by U.S. workers followed in coming decades, including a walkout by Arab workers in 1967 protesting U.S. support of Israel during the Six Day War and millions of black workers protesting after the assassination of Martin Luther King Jr.
In 2006, the focus of May Day demonstrations shifted to immigration when roughly 1 million people, including nearly half a million in Chicago alone, took to the streets to protest federal legislation that would have made living in the U.S. without legal permission a felony.
Immigration-themed May Day gatherings dwindled since but are expected to ramp up Monday as groups protest executive orders signed by Trump and seen as attacks on immigrants' rights.
Durand, the Washington-based organizer, said her group’s march will start at Dupont Circle, travel down to Lafayette Square near the White House and culminate with speeches from immigrants and elected officials. Marchers will be joined by other groups, swelling their numbers by tens of thousands, she said. More than 200 immigrant-owned businesses in the area will also shut down.
“We’re going to be able to show we are one voice, one people speaking for those whose lives are being trampled on,” Durand said.